The yield and quality of desired plant products is determined by the health of the plant. A healthy plant is one which is able to withstand biotic (pathogens, insects, etc.) stresses as well as abiotic (cold, heat, drought, etc.) stresses. Conversely, a weak plant is one which succumbs to pathogen and/or environmental stresses. During imbibation, dry seed experiences stresses due to sudden rehydration. These stresses can impact both the extent and speed of seed germination. A healthy seed is one which is able to germinate faster and thus get a head start. Such a head start improves the seed's chances of increasing its yield, especially in areas with shorter growing seasons. The commercial value of seed is determined in part on percentage (%) germination, rate of germination and the robustness of the seedling produced. There is a great interest in improving these properties of commercial seeds.
Mature seeds of most crop plants contain very little moisture. These seeds can be stored for a long time in dormant stage. The living portion of the seed, the embryo, remains inactive in dehydrated state as long as the seed is remains dry. When these seeds are sown in the soil a rapid rehydration occurs. During this process, the embryo cells rehydrate and expand. Cell membranes are assembled into an organized structure that preserves the integrity of the cells. However, since rehydration is generally quick, the cell membrane is not fully assembled in the initial phase of rehydration. This results in some leakage of cellular contents. During rehydration, since membranes are ‘leaky’. Important molecules, including proteins, carbohydrates and inorganic molecules, are known to leak in the initial phase of rehydration. This leakage of important cellular constituents is known to cause injury or stress to the embryo. Leakage of cellular constituents has been associated with the failure of seeds of many crops plants to germinate and/or produce healthy seedlings. Many seeds fail to germinate if the leakage of cellular solute is significant. “Seed priming” is intended to impart “health” to the embryo cells so that leakage (thereby injury) to the embryo can be minimized.
The injury of crops as a result of abiotic and biotic stresses has been a major problem in the agricultural production areas of the U.S. Specifically, over 60% of the crop loss for last 50 years has been due to abiotic stresses (see USDA Agricultural Statistics, 1998). Abiotic stresses include chilling, freezing, drought, heat, and other environmental factors. In 1996, the loss of crop yield due to abiotic stresses was recorded to be more than a billion dollars in the U.S. (see USDA Agricultural Statistics, 1998). Thus, there is a tremendous interest in the plant industry to find a technology that can be used to prevent or mitigate stress injury and to accelerate recovery following a stress injury.
Lysophospholipids are derived from membrane phospholipids by the removal of a fatty acid by the action of an enzyme phospholipase A2. Lysophospholipids are naturally present in plant and animal tissues, and can be found in high concentrations in egg yolk, brain tissue, and soybeans. Lysophospholipids are available commercially from Avanti Polar Lipids, Inc. (Alabaster, Ala.) and from Sigma Chemical Co. (St Louis, Mo.). Lysophospholipids, such as lysophosphatidylethanolamine (hereinafter referred to as “LPE”) and lysophosphatidylinositol (hereinafter “LPI”), have been exploited for accelerating fruit ripening, enhancing fruit stability during storage, and increasing the shelf life by retarding senescence of plant tissues such as fruits, vegetables, and cut-flowers. Farag, K. M. et al., Physiol. Plant, 87:515-524 (1993), Farag, K. M. et al., HortTech., 3:62-65 (1993), Kaur, N., et al., HortScience, 32:888″890 (1997), Ryu, S. B., et al., Proc. Natl. Acad. Sci. USA, 94:12717-12721 (1997). Methods for using LPE to enhance fruit ripening and storage stability are disclosed in U.S. Pat. Nos. 5,126,155 and 5,100,341. Methods for using LPE with 18:1 fatty acid and LPI to retard senescence and to enhance fruit ripening is described in WO 99/23889.